This invention relates to a method for removing mineral and other deposits from hard surfaces such as glass, tile and the like and compositions for such use.
In the many parts of the country, it is common to find water containing calcium, magnesium or iron (II)ions in solution. Calcium ions derived from the passage of natural waters through and over limestone are the most common metallic ions in "hard water". Under certain conditions, insoluble salts of these metals precipitate.
Hardness in water is objectionable for several reasons. Deposits of insoluble metallic salts may be precipitated when water is heated or when soaps are added, prior to cleaning of the surface. The deposition of insoluble salts is also especially problematic when hard water comes into contact with mirrored glass and tile surfaces. In particular, mirrored glass is used in supermarket produce cases to reflect the vegetables and to enhance the display. A misting system is commonly used in produce cases to automatically spread water onto vegetables several times each hour to help retain their freshness. Typical produce cases keep refrigerated air constantly moving over the produce and over the mirrored glass surface. The moving air causes some of the water to evaporate between the misting cycles and leads to deposition of the minerals and other foreign matter on the mirrored surface. After several weeks this buildup is difficult to remove with conventional cleaning products and techniques. The buildup gives the mirror the appearance of being dirty and, because of the proximity of fresh produce, it presents an unacceptable situation with respect to the customers' perceptions of the store and its environs.
Various methods have been employed to prevent this problem by attempting to remove the minerals from the water using ultrafiltration, reverse osmosis and deionization systems. These methods are only partially successful because they cannot remove all of the minerals economically and thoroughly. Other methods such as removing the mirrors from the supermarket produce case entirely and cleaning them with acid has proven to be costly and hazardous to the health of the personnel. Attempts to remove the deposits (i.e. scale) with steel wool typically damage the glass surface.